The present invention relates to a cassette device for producing digital images, for a radiography apparatus. In general, such radiography apparatuses comprise an X-ray emitter, a device for supporting the cassette for producing images, the organ to be radiographer being arranged between the X-ray emitter and the cassette support device, a means for processing the data thus obtained and a space for storing the cassette when it is not being used.
By way of example, there are known mammography apparatuses which comprise an X-ray source arranged on one side of the organ to be radiographer, a support table, transparent to X-rays, arranged on the other side of the organ to be radiographer, an adjustable holding plate which presses the organ onto the support table, and a housing for receiving a cassette for producing images containing an exposable film. The housing is arranged under the support table and constitutes a means for receiving the cassette. After an image of the organ has been taken, the cassette containing the exposed film is extracted from its housing, and the film is developed.
Such apparatuses are generally used for finding possible symptoms of breast cancer. With the aim of reducing the time for which the patient is immobilized, the cassette containing exposable films may be replaced by cassettes containing a means for producing digital images, capable of producing images extremely quickly. The image production operations, in particular during a biopsy, are thus much shorter and reduce the discomfort of these examinations. Furthermore, cassettes for producing digital images allow the quality of the diagnosis to be improved. For economic reasons, it is desirable to use cassettes for producing digital images without changing the rest of the radiology apparatus. The cassette should be removable, so that it can be arranged either under the table, during diagnosis, or in the puncture system, during a biopsy.
A cassette for producing digital images comprises a casing, within which a device for detecting the radiographic signal is arranged. This detection device may, for example, comprise a scintillator capable of converting the incident X-rays into light radiation, an optical fiber making it possible to filter most of the X-radiation which has passed through the scintillator, and protecting the components located downstream of said optical fiber, and a charge-coup]Led device (CCD) array camera forming a sensitive region. In order to ensure that the cassette is positioned appropriately in the housing, the cassette is generally provided with a locking means. The cassette is also provided with an electrical cable connecting it to a data processing means, In general a microcomputer.
A mammography apparatus is generally provided with a support table whose height can be adjusted, and an X-ray source which can be tilted through .+-.180.degree. relative to the vertical plane of symmetry of the apparatus. The support table may be replaced by a puncture system, intended for biopsy and also provided with a reception means. The puncture system comprises a holding plate which acts as a compression pad, a needle holder and a needle capable of performing a biopsy in the organ to be radiographer.
The data processing means may be connected to the puncture system and to the cassette by electrical cables, in particular in order to process the data received from the cassette and to control the puncture system, in particular the movement of the needle holder during biopsy. The data processing means can also control the X-ray source and comprises a screen for displaying the images of the radiographer organ and a keyboard. The data processing means may be equipped with software intended for the calculations of the three-dimensional coordinates of points in the organ to be radiographer on the basis of two images produced at different angles by virtue of the pivoting of the X-ray source. It is thus possible to obtain excellent visualization either of particular regions in the radiographer organ during diagnosis, or of the positioning of the needle in the radiographer organ during a biopsy, by using optimized display methods.
During operation, the X-rays are emitted by the source, passed through the holding plate, the radiographed organ, the breast support: plate and the upper wall of the sensitive region of the cassette, and enter the scintillator which, on receiving X-rays, emits visible light which is forwarded to the array camera by the fiber-optic layer. The array camera makes it possible to convert the information received in the form of visible light into information in the form of a digital electrical signal, which is transmitted to the data processing means.
Conventional digital cassettes are expensive and are not very easy to handle because of their flat shape and their attachment to an electrical cable connected to the data processing means. Twisting the cable close to the cassette, or sudden pulling risks causing significant damage inside said cassette. The risk of dropping should also be avoided. Furthermore, precise and secure positioning of the cassette in a housing is not obtained with conventional cassettes because of the presence of the cable. However, precise positioning is important for the quality of the images obtained, to avoid blurring, and for the accuracy of the positioning calculations for the biopsy examinations.
The object of the present invention is therefore a cassette device for producing images which overcomes the above drawbacks, which is easy to grip, whose positioning is precise and whose cable outlet is protected.
The cassette device for producing images according to the invention is intended for a radiography apparatus of the type comprising a means for receiving mobile cassettes. The cassette comprises a casing of substantially parallelepipedal shape surrounding a means for producing images. The device comprises a means which forms a handle and is arranged on a small face of the casing, said means forming a handle being provided with a stop surface for insertion of the cassette into the reception means of the radiography apparatus. The means which forms a handle may comprise a surface for supporting the arm of a patient being radiographed, and a cable outlet. The risk of the cassette slipping from the hands of an operator is thus greatly reduced. Possible twisting of the cable close to the cassette, or pulling will not have detrimental effects inside the casing, since the corresponding forces are taken up by the means which forms a handle. There is no longer any risk of the patient's arm being in direct contact with the cable.